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A023252 Numbers n such that n remains prime through 2 iterations of function f(x) = 5x + 2. 5
13, 19, 31, 79, 97, 199, 331, 349, 373, 457, 541, 577, 607, 643, 709, 769, 811, 859, 1021, 1069, 1171, 1249, 1321, 1381, 1447, 1483, 1693, 1867, 2113, 2137, 2239, 2539, 2719, 3037, 3061, 3163, 3181, 3187, 3313, 3433, 3463, 3673, 3727, 3853, 3919, 4021, 4639 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

n, 5*n+2, 25*n+12 are primes. - Vincenzo Librandi, Aug 04 2010

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

MATHEMATICA

Select[Prime[Range[1000]], And@@PrimeQ[NestList[5#+2&, #, 2]]&] (* Harvey P. Dale, Nov 24 2012 *)

PROG

(MAGMA) [n: n in [0..100000] | IsPrime(n) and IsPrime(5*n+2) and IsPrime(25*n+12)] // Vincenzo Librandi, Aug 04 2010

CROSSREFS

Sequence in context: A163847 A051644 A101408 * A279426 A241120 A128342

Adjacent sequences:  A023249 A023250 A023251 * A023253 A023254 A023255

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified December 15 20:00 EST 2019. Contains 330000 sequences. (Running on oeis4.)